The invention relates to a method for assisting a driver of a motor vehicle during a driving procedure to overcome a low-level obstacle at slow velocity, and also a control unit, which is designed for the purpose of executing such a method.
When driving using a motor vehicle having a conventional manual shift transmission and internal combustion engine, the driver manually controls, in cooperation with the accelerator pedal and clutch, a start procedure from a standstill over an obstacle (for example, a curbstone), such that a high torque is initially transmitted to the wheels with low clutch slip, in order to overcome the obstacle without stalling the engine. After overcoming the obstacle, the driver opens up the clutch again himself, as soon as the vehicle is set into motion, so that the traction is interrupted again and the vehicle rolls away rapidly.
In a motor vehicle having an automatic transmission with a torque converter, as a result of the characteristic of the torque converter, moderate torque is unfolded as a curbstone is overcome, so that it can be overcome in a controlled manner and with continuous, smooth forward movement of the motor vehicle.
In contrast, the start procedure using an electric vehicle over a stepped obstacle has heretofore been problematic. The driver also initially requests an elevated torque here to overcome the obstacle, by actuating the accelerator pedal. During the travel after overcoming the obstacle, the vehicle suddenly accelerates forward, since the high torque which was built up still acts on the driven wheels. Heretofore it has not been possible to control those driving situations safely and reliably in electric vehicles, in which the electric vehicle accelerates strongly from slow travel in the desired travel direction in such a manner that an excessively high velocity is reached. A relatively long time can pass until the driver has overcome the moment of surprise and reacts appropriately (for example, brakes). Therefore, the acute danger exists of a collision with another vehicle close to the obstacle, for example.